van der Eijk: Mente e cérebro na medicina antiga

It can be inferred from remarks made by Plato, Aristotle   and in the Hippocratic Corpus [1] that as early as the fifth century bce doctors and natural philosophers disagreed on the question which bodily factors (organs, tissues or substances) played the most important part in performing faculties we would call ‘psychic’ or ‘mental’. These include thinking, perception, feeling, remembering, and so on. Secondary literature on this issue usually distinguishes between the encephalocentric, cardiocentric and haematocentric view on the seat of the mind. [2] The encephalocentric view was allegedly [125] taken by the fifth-century medical writer Alcmaeon of Croton (South Italy), who was thought to be the first to discover the existence of the optic nerve, by the author of the Hippocratic work On the Sacred Disease, and by Plato (in the Timaeus  ). The cardiocentric view was represented in the Hippocratic writings On Diseases 2 (fifth century bce), On the Heart (end of the fourth/start of the third century bce) and by Aristotle, Diodes of Carystus and Praxagoras of Cos (fourth century bce). The haematocentric view was taken by Empedocles   and the authors of the Hippocratic writings On Diseases 1 and On Breaths (all fifth century bce). Although this division may be largely appropriate in terms of the period concerned, it is already too much a product of the schematisation mentioned above, which became characteristic of the debate in later doxography. Strictly speaking, only the authors of On the Sacred Disease and On the Heart express an opinion on the location of what they consider the highest psychic faculty, the former choosing the brain, the latter the heart. Apart from this, the division into three areas presents the matter in too static a way: most of the authors mentioned appear to regard psychic activities mainly as processes, in which some parts of the body are more involved than others, but which are in principle based on the interaction between a number of anatomical and physiological factors.

It would be better to ask in which terms ancient doctors from the fifth and fourth centuries bce thought about these matters, and which types of arguments they used to substantiate their views. The following categories can be discerned:

faculties (thought, perception, feeling, etc.)
parts of the body (heart, brain, diaphragm, etc.)
substances (blood, air, phlegm, etc.)
processes (decay, constipation, etc.)
relations/proportions (balance, mixture, etc.)

In the discussions which doctors devote to the subject, they employ terms that on the one hand refer to a certain part of the body or otherwise anatomical-physiological material, and on the other hand to an activity or faculty exercised or enabled by it: the part of the body contributes to’, is ‘the instrument of’ or ‘the material substrate of’ a ‘faculty’ or ‘ability’. It is not always immediately obvious to what extent the medical authors made a distinction between ‘mental’ processes as such and physiological processes. [3] Most authors of the Hippocratic Corpus appear to assume a kind of continuum between body and mind: in lists of symptoms, psychological phenomena are mentioned among purely physical ones without any [126] categorical difference, and the cause for mental disorders is virtually always sought in bodily factors.

Mental faculties are given a more independent role in the Hippocratic writing On the Sacred Disease, in which the function of the brain is characterised as ‘interpreting’ (hermeneus) what is derived from the air outside. This is in many respects a key text, not least because of the authors polemic stance to rival views:

For these reasons I believe that the brain is the most powerful part in a human being. So long as it is healthy, it is the interpreter of what comes to the body from the air. Consciousness is provided by the air. The eyes, ears, tongue, hands and feet carry out what the brain knows, for throughout the body there is a degree of consciousness proportionate to the amount of air which it receives. As far as understanding is concerned, the brain is also the part that transmits this, for when a man draws in a breath it first arrives at the brain, and from there it is distributed over the rest of the body, having left behind in the brain its best portion and whatever contains consciousness and thought. For if the air went first to the body and subsequently to the brain, the power of discerning thinking would be left to the flesh and to the blood vessels; it would reach the brain in a hot and no longer pure state but mixed with moisture from the flesh and from the blood so that it would no longer be accurate. I therefore state that the brain is the interpreter of consciousness.

The diaphragm (phrenes), however, does not have the right name, but it has got this by chance and through convention. I do not know in virtue of what the diaphragm can think and have consciousness (phronein), except that if a man suddenly feels pleasure or pain, the diaphragm leaps up and causes throbbing, because it is thin and under greater tension than any other part of the body, and it has no cavity into which it might receive anything good or bad that comes upon it, but because of the weakness of its structure it is subject to disturbance by either of these forces, since it does not perceive faster than any other part of the body. Rather, it has its name and reputation for no good reason, just as parts of the heart are called auricles though they make no contribution to hearing.

Some say that we owe our consciousness to our hearts and that it is the heart which suffers pain and feels anxiety. But this is not the case; rather, it is torn just like the diaphragm, and even more than that for the same reasons: for blood vessels from all parts of the body run to the heart, and it encapsulates these, so that it can feel if any pain or tension occurs in a human being. Moreover, it is necessary for the body to shudder and to contract when it feels pain, and when it is overwhelmed by joy it experiences the same. This is why the heart and the diaphragm are particularly sensitive. Yet neither of these parts has any share in consciousness; rather, it is the brain which is responsible for all these. (16-17 [6.390-4 L.]) [4]

[127] This passage is part of a rather complicated explanation of epilepsy (for details on this see the next paragraph). The brain plays a pivotal role in this explanation as it is the point from where bodily and psychic faculties are co-ordinated, but also because it is particularly sensitive to harmful influences from the environment, such as climate and season (‘so long as it is healthy). These influences can therefore be additional factors that contribute to the course the disease takes. The author emphasises this crucial role of the brain as part of his polemic against two rival factions which consider the diaphragm or the heart to be the central organ that is the source of consciousness. He dismisses the etymological argument of the first faction (phrenes — phronesis) as invalid, and accommodates the empirical fact that both factions put forward — the hearts leaping in case of sudden gladness or sadness — into his own theory, which is also based on empirical observations (namely the delicacy of the diaphragm and the veins going to the heart). In a previous chapter he employed an empirical argument to support his conviction that the disease is caused by an accumulation of phlegm in or around the brain. He claimed that if one were to open the skull of a goat that died as a result of an epileptic fit, one would find a large amount of fluid (phlegm) around the brain. [5]

It is striking that a distinction is made here between consciousness’ (phronesis) and understanding’ (sunesis): the latter is apparently related to the ‘discerning thinking’ (diagnosis) which is mentioned later in the text, and which requires a certain degree of purity and precision that is adversely affected by contact with organs and tissues. In this context phronesis clearly means more than ‘thinking’ or ‘intelligence’, as the word is commonly translated. It means ‘having one’s senses together’ and refers to a universal force by which a living being can focus on its surroundings and can undertake activities; it also implies perception and movement. [6] [7] Phronesis can be found throughout the body, whereas ‘understanding’ is restricted to the brain. Another thing that is striking is that the author is of the opinion that the brain is also the source of feeling — although he admits that the heart and diaphragm take part in this as well.

A text in which mental phenomena are even more clearly classified as a separate category is the Hippocratic writing On Regiment The author, a particularly ‘philosophically inspired mind, presents psuche (sometimes [128] also referred to as dianoia) as a distinct entity, separate from the body (soma). This distinction manifests itself in particular during sleep (4.86-7). However, this does not imply that the soul is immaterial. The soul consists of water and fire (the elements which, according to this author, have the greatest influence on the constitution of the human body), which stand in a certain proportion to each other. Fluctuations in this proportion result in differences between individual people’s cognitive skills, such as acuteness, a good memory, precision of the senses and proneness to certain emotions (1.35). When the balance between these two elements is seriously disturbed, it will give rise to psychological disorders, but these can be cured by changing eating and drinking habits and adopting a certain lifestyle (1.36). According to this author, the soul is therefore a material entity, yet it does not have a fixed location: it moves through the body via ‘passages’ (poroi). The condition of these passages (for instance their width or narrowness) is a further influential factor in someone’s mental functioning. In the state of wakefulness, the soul distributes itself over the entire body and carries out certain tasks ‘for the benefit of the body’, including hearing, seeing, touching and movement. During sleep, or rather ‘when the body is asleep’, the soul remains awake and withdraws in its own ‘home’ (oikos), where it carries out the activities of the body independently. These include seeing, hearing, walking, touching, grieving, thinking: they are called enhupnia or ‘dreams’. Yet the author does not venture an opinion on the location of the soul and its ‘home’.

A presentation like this shows how inadequate terms like ‘materialism’ and ‘dualism’ are to describe ancient theories on body and mind. The author of On Regimen may be called a materialist to the extent that he holds an entirely material view on the soul; yet at the same time he assumes two separate entities which may normally co-operate and mutually influence each other, yet one of them (the ‘soul’) can also function independently, as, for instance, in sleep. [8]

The greatest refinement in the definition of the status of mental phenomena can be found in Aristotle, although his comments on the topic, too, show a certain amount of fluctuation. He expresses the view that the ‘soul’ is not a separate entity, which might exist independently of the body: ‘soul’ to Aristotle is ‘the form of the body’, that which causes a body to live, which gives it structure and enables it to exercise its faculties. [9] Yet this [129] does not prevent him from repeatedly speaking of experiences typical to the soul’, activities a human being carries out ‘with his soul’, or perceptions which ‘penetrate the soul’. According to Aristotle, the functioning of the dual entity that body and soul constitute is governed by a large number of organs and material factors. The heart is assigned the role of‘beginning’ or ‘origin’ (arche), both as a source of essential bodily heat (required among other things for the digestion of food) and as the seat of the central sense organ, which is connected with the limbs and the separate sense organs and co-ordinates the data it receives from them. [10] Furthermore, in exercising this co-ordinating task the heart is supported by the blood (as a medium for transporting sensory information) and air (pneuma, for the transmission of motor signals). Their role is important, yet not fully defined. [11] The size of the heart, which differs in each species of animal, has an influence on certain character traits and on susceptibility to certain emotions; [12] the condition of the blood (pure, turbid, cold, hot) influences the quality and speed of sense perception. [13] The brain is not involved in all this: it has no cognitive faculties and serves only as a chilling element in the body, for tempering the heat that radiates from the heart. [14]

An even more elaborate physiological theory is presented by Diodes of Carystus (fourth century bce). He assumes interaction between the heart (to him the real seat of the mind), the brain (which plays a pivotal role in sense perception) and the so-called ‘psychic pneuma’, a delicate substance that is responsible for transmitting sensory and motor signals. [15]

It is clear, then, that many medical authors of the fifth and fourth centuries bce assume a cognitive centre somewhere in the body from where abilities such as perception and movement are ‘transported’ or ‘transferred’ to peripheral organs. Organs for perception, limbs and other parts of the body are assumed to be connected to each other and to a centre via certain ‘passages’ (poroi, phlebes, neura). [16] Through these passages air or blood are conducted; an accumulation of certain bodily fluids (such as phlegm or bile) can cause the passages to get blocked. The assumption of the existence of this network of passages and the ideas about their course and ramifications are highly speculative and hardly based on what we would [130] call focused anatomical research. [17] More elaborate views on the network of cognitive faculties in the body are only rarely based on empirical observations, as in the case with the above-mentioned Alcmaeon, who is believed to have arrived at an encephalocentric view on the mind on the basis of the connection between the eyes and the brain. Yet the fact that this observation was known both to the author of the Hippocratic work On Fleshes and to Aristotle, who nevertheless do not attribute any significant role in cognition to the brain, proves that it might equally give rise to other interpretations.

The authors mentioned do in fact employ rather sophisticated terminology for what we would call psychological, mental or spiritual faculties, but they assume a close connection between these faculties and anatomical and physiological factors. When speaking about exercising these faculties, they virtually always do so in terms of certain substances (such as blood, air or water) or qualities (hot, cold, dry, wet) and of processes such as flowing and distributing or, in case the psychic faculties have been disturbed, of stagnation, constipation, blockage, and so on. Another recurring element is the emphasis on balance (isonomia, summetria, eukrasia) and on the risk of an excess or shortage of a certain substance or quality.

An exception to this rule is Aristotle’s idea that the highest cognitive faculty, thought, is not bound to a physical substrate. It is a kind of epiphenomenon that, although it is unable to function without sense perception (and therefore without physiological processes), cannot be located in a particular place of the body. [18] For this reason it is, strictly speaking, not correct to attribute a cardiocentric view on the mind to Aristotle, as has frequently been done both in antiquity and in modern literature. [19] The only text in which the mind is explicitly located in the heart is in the Hippocratic work On the Heart, which offers a remarkably detailed description of the anatomy of the heart. The author of this presumably post-Aristotelian writing claims that gnome (‘mind’, ‘insight’) has its seat in the left ventricle of the heart, from where it issues its decrees about ‘the other (part of the) soul’ (alle psuche), which is situated in the rest of the body. To prove his stance, the author argues that if autopsy were carried out on a body of a living being that had just been killed, the aorta would still contain blood, but the left [131] ventricle would not; [20] this maintains contact with the blood by means of a process of ‘evaporation’ and ‘radiation’.